How to get a watertight seal

I broke a braided hose broke on the hot connection to the kitchen tap over the weekend.

I've replaced the horrible screwdriver shutoff valve with a handled version and also used new copper pipes.

Problem is I get a leak in two places - one at the top connection of the shutoff valve (I used ptfe tape on the thread and screwed it really tight. And one where the copper pipe connects to a plastic elbow joint (rubber o-ring with a plastic collar and plastic screwtop).

Now the o-ring seal did work fine before I replaced the copper pipe, so that kind of points to me doing something wrong. (using a junior hacksaw not the best for cutting copper pipe but my cutter broke so i'll get a new one).

the copper pipe might be deformed by your hack sawing. i think you need to re-cut copper pipe with proper pipe cutter. that is why you not getting good seal on the elbow joint.always show picture so that people are not gussing what you have done.

16th Jan

you don't need PTFE on the thread, just the olive.

16th Jan

where exactly is it leaking from ?

16th Jan

The junior hacksaw cut has likely damaged the o ring of the plastic fitting, you will need to buy a new one. Make sure you file the copper pipe neatly to ensure no burrs damage it again (or just buy a cutter at the same time).

Agree about the ptfe, it should go around the olive, if you really must use it. I find it more successful to compress the olive, then undo and wrap it with PTFE, then re-do.

16th Jan

Also you said you tightened the new valve really tight. If you use a copper olive and tighten too much you can crack the olive and it will leak. Whilst you don't need to use PTFE tape I find its best to use on all compression joints and NOT overtighten them. Replaced my own kitchen tap at the weekend and agree the service valves which need a flat screwdriver to turn them on and off are not so good, especially in hard water areas. I had one of these fail and caused a right mess of my sink unit. It as leaking out of the valve where the screwdriver slot is.

16th Jan

Never use ptfe tape. Useless stuff I find and only use as a last resort which nearly always fails. Only ever use successfully on radiators. When using compression fittings if you put a tiny bit of Vaseline on the thread it makes doing up the nut easy. Can use just your hands to get it most of the way. I just nip um up then. Sounds like you have over tightened the joint causing a leak

Edited by: "wayners" 16th Jan

16th Jan

Threadlock is rubbish as well so don't bother. Same goes for split washers and nyloc nuts. They are all pretty damn useless for leaks and stopping things from coming loose. And if ever you're bolting anything together throw the washers away and just let the bolts heads dig into the material you're fastening together. All of which is pretty useless advice and incorrect but then those who never took an engineering apprenticeship always know best.

The use of ptfe tape is an individual choice. There are no hard and fast rules. Modern compression fitting which are not tapered threads don't insist or require the use of it. However, you will always get the odd fitting or olive that is slightly sub-standard which you can't tell with the naked eye and the surface don't mate properly when you nip them up. Most times a couple of wraps with ptfe turned CLOCKWISE will stop a weepy joint from leaking. If you don't wrap it clockwise you're wasting your time. If you don't want to use PTFE then change the olive. Eventually copper compression fittings will become less and less popular. The rebuildable plastic fittings not push fit are so much better. No spanners required and you can't over tighten them by hand.

Original Poster17th Jan

Thanks for the replies, any recommendations for photo sharing sites so I can upload pictures?

I used sandpaper to clean up the copper pipes so there were no sharp edges so the rubber o-ring will not be damaged, I tightened that seal by hand so it shouldn't be over tight.

I will pick up a rated cutter tomorrow from Screwfix (Rothenburger £16.99)

Original Poster17th Jan

tomminator

where exactly is it leaking from ?

Edited by: "Bigfootpete" 17th Jan

Banned
17th Jan

Bottom leak is either you have bent the copper OR not pushed it into the fitting properly

Top leak is either you have bent the copper, or not pushed it into the fitting properly OR not tightened it enough or over tightened. (I presume you did use an olive)

As other have said. You dont use tape on the thread. You wrap it around the side of the olive nearest the fitting but if you do your job properly you do not need tape.

Original Poster17th Jan

YouDontWantToKnow

Bottom leak is either you have bent the copper OR not pushed it into the … Bottom leak is either you have bent the copper OR not pushed it into the fitting properly Top leak is either you have bent the copper, or not pushed it into the fitting properly OR not tightened it enough or over tightened. (I presume you did use an olive) As other have said. You dont use tape on the thread. You wrap it around the side of the olive nearest the fitting but if you do your job properly you do not need tape.

Thanks, that's what I thought might be the case for the bottom fitting - I may have to cut a longer section of copper pipe to re-do that bit. I didn't know it was called an olive, but yes I did use one on the top fitting. I'll also re-connect, but not sure how loosening the nut will make it more watertight? (I certainly don't want to make it any tighter.)

Banned
17th Jan

Bigfootpete

Thanks, that's what I thought might be the case for the bottom fitting - … Thanks, that's what I thought might be the case for the bottom fitting - I may have to cut a longer section of copper pipe to re-do that bit. I didn't know it was called an olive, but yes I did use one on the top fitting. I'll also re-connect, but not sure how loosening the nut will make it more watertight? (I certainly don't want to make it any tighter.)

The bottom fitting needs to be forced in. You think they are in but if you push a bit further you will feel a click & it will slide in another 1cm.

Banned
17th Jan

Bigfootpete

but not sure how loosening the nut will make it more watertight? (I … but not sure how loosening the nut will make it more watertight? (I certainly don't want to make it any tighter.)

You cant loosen it now. If it is due to overtightening you will need to swap the pipe for a new piece. Overtightening can bend/crush the pipe & the olive.

Banned
17th Jan

Oh. & also on the bottom leak there is a slight possibility you have damaged the o-ring in the fitting.

This can happen if you didnt de-burr the copper pipe after cutting.

Original Poster17th Jan

YouDontWantToKnow

Oh. & also on the bottom leak there is a slight possibility you have … Oh. & also on the bottom leak there is a slight possibility you have damaged the o-ring in the fitting.This can happen if you didnt de-burr the copper pipe after cutting.

I did, thoroughly sanded the end of the pipe so that it was smooth, should be ok but I'll check.

Banned
17th Jan

Bigfootpete

I did, thoroughly sanded the end of the pipe so that it was smooth, … I did, thoroughly sanded the end of the pipe so that it was smooth, should be ok but I'll check.

Well you can rule that out as a cause.

Original Poster20th Jan

Once I got a decent pipe cutter I re-cut slightly longer pieces of copper and reconnected everything using ptfe tape around the olives as suggested, jobs a goodun!